FIG. 1 illustrates the well known basic circuitry of a modern slot machine 10 which incorporates rotating reels. In such a slot machine 10, each of the reels 12, 13, and 14 has a variety of symbols printed on its periphery. Each of the reels 12-14 is driven by a separate stepper motor 16 which rotates in response to pulses from a CPU 18. When the pulses to a stepper motor 16 are terminated, the reel stops abruptly.
In modern slot machines, the stopping positions of the reels 12-14 are predetermined using a random number generator consisting of a random number generator program in the program ROM 20 carried out by the CPU 18. The required number of pulses to the three stepper motors are then generated to display the symbol combination at the predetermined reel positions.
In one common type of slot machine, the number of pulses after the reel has reached a zero position are counted to determine the final position of the reels. In another type of machine, each of the reels has tabs that are sensed by a photodetector to determine the angular displacement of the reel and thus the final displayed symbol. Other means for detecting the positions of the reels exist and are well known.
A money detector 22, which may detect coins or other currency, issues a command to the CPU 18 that the slot machine 10 is ready to be played. The player may then pull a handle 24 or press a button to initiate play.
After the reels have stopped, and the CPU 18 determines the final stop positions, the stop positions are then applied to a pay-table ROM 26, which cross-references the final displayed symbols with a monetary payout to the player. This payout is then conveyed to a payout mechanism 28 which issues coins or credits to the player. A display 30 may also be activated, signaling a win to the player.
The above general description of a modern slot machine would be well known in the art, and such a programmable machine offers great advantages. Slot machines are varied by simply changing the operating program in the program ROM 20 and the award program in the pay-table ROM 26. The front glass of the slot machine is also changeable to convey particular features of the machine.
Additional detail of such conventional slot machines is found in U.S. Pat. No. 4,095,795 to Saxton et al.; U.S. Pat. No. 4,448,419 to Telnaes; and U.S. Pat. No. 4,573,681 to Okada, all incorporated herein by reference.
One well known award criterion for a 3-reel slot machine is the matching of symbols in a horizontal direction. After each game, the player again pulls the handle so that each game is completely independent of all previous games.
Although the slot machine of FIG. 1 is very successful, even more player appeal would be created by allowing the player additional possibilities for winning.